1. Field of the Invention
This invention relates to a dye transfer sheet for use in sublimation heat-sensitive transfer recording.
2. Description of the Prior Art
Heretofore, techniques for color recording facsimile printers, copying machines, television images etc. have been sought, and color recording techniques by electron photography, ink-jet process, heat-sensitive transfer etc. have been under study.
The heat-sensitive transfer recording process is considered more advantageous as compared with other processes since the maintenance and operation of the device are easier and the device and expendable supplies are less expensive.
The heat-sensitive transfer process is roughly classified into two processes, that is, a molten heat-sensitive transfer recording process which comprises heating a transfer sheet having a heat-melting ink layer formed on a base film by a heat-sensitive head to melt said ink thereby transfer recording onto a recording body, and a sublimation heat-sensitive transfer recording process which comprises heating a transfer sheet having an ink layer containing a sublimable dye formed on a base film to sublime the dye thereby transfer recording onto a recording body.
And, said sublimation heat-sensitive transfer recording process is believed suitable for full color recording since it is possible to control the amount of the dye to be sublimed and transferred by controlling the energy applied to the heat-sensitive head and hence gradation expression is easy.
In general, full color recording is conducted by using tricolor dyes, that is, a cyan color dye, a magenta dye and a yellow color dye, and sometimes, four color dyes, that is, these three plus a black color dye, but in order to obtain full color recording having good color reproducibility, the following requirements must be satisfied: the respective dyes easily sublime under the operational conditions of the heat-sensitive recording head, do not undergo thermal decomposition under the operational conditions of the heat-sensitive recording head, have preferred hues for color reproduction, have great molecular absorption coefficients, are stable against light, moisture, chemicals etc., are easily sythesized, have excellent adaptability to inks, etc.
However, no conventional cyan dye has satisfied the above requirements.
Accordingly, one object of this invention aims to provide cyan color dyes which fulfill such requirements that they easily sublime under the operational conditions of the heat-sensitive recording head, do not undergo thermal decomposition under the operational conditions of the heat-sensitive recording head, are stable against light, are easily synthesized, are readily and uniformly dissolved or dispersed to prepare an ink of a high concentration, etc. Another object of this invention is to provide a dye transfer sheet which has an ink layer containing such cyan color dyes coated on a base film.